It is known to a person skilled in the art that a transparent film, e.g. a photoresist film formed by applying a resist, e.g. in a manufacturing process of semiconductor devices to form a multitude of semiconductor devices on a semiconductor wafer cut out from a single crystal lot, is selectively etched to form first conductive semiconductor layers, electrodes and leads of desired shapes. Mask alignment is performed in every one of these steps. Since a state of a resist surface, e.g. a change in film thickness, foreign matters, scratches cause semiconductor defects, they are requested to be found in early steps.
The photoresist spreads to form a thin coating on the surface by rotating the wafer about a center axis at a high speed. Due to an edge surface effect, the photoresist deposits on the edge of the wafer. Thus, it is known to be necessary to remove the photoresist on the edge (EBR process).
Accordingly, there has been provided an inspection method for inspecting the perfection of the photoresist removal and a predetermined position of a boundary line between an area including the photoresist and an area not including the photoresist, i.e. an edge bead removal line (EBR line) (JP2006-352113A). In this JP2006-352113A, an image area on a surface of a wafer is irradiated using light in a wavelength range of 360 nm to 500 nm and a fluorescence image in the image area is reflected from fluorescent light emitted due to irradiation by excitation light to identify a fluorescent EBR line.
However, since a dark-field image is obtained in JP2006-352113A, resolution (resolving power) itself is not improved. A feature of a dark-field illumination method is that the use is basically difficult for thick specimens. Further, it is necessary to use a photoresist added with a fluorescent dye and a fluorescent EBR solution. In inspecting the coating film of the photoresist, there is a disadvantage that an arbitrary inspection target cannot be dealt with if the coating film itself requires ingenuity.
Further, a device with a CCD camera extending over an entire substrate surface is provided as a substrate inspection apparatus (JP2009-10349A). By plotting data on polar coordinates, a substrate to be rejected is selected which has a risk of increasing contamination due to the overlap of lines corresponding to a BARC layer, a top coat layer and a resist layer on an edge part of the substrate.
However, it is only mentioned in JP2009-10349 to select a substrate having an overlap on an edge part in each layer as a substrate to be rejected. Thus, although it is mentioned to fit a curve to data for automatic analysis in addition to visual judgment in testing a substrate, it is not clear how automatic analysis is performed other than based on the overlap on the edge part. Therefore, there has been room for improvement as to whether or not promotion of streamlining is possible.
Further, an edge feature measurement system has been provided which detects a relative distance from an edge part of a wafer to that of a resist layer via an imaging system (JP2009-544157A). In this system, pixel arrays having a plurality of first dimension X and second dimension Y are acquired around a wafer edge area and an edge map is generated from the respective pixel arrays. The intersection of a layer is evaluated and measured or another characteristic is determined from an image covering around the wafer.
However, these systems are complicated since an image is generated by mapping. Specifically, an overall evaluation cannot be made unless the edge map is completed. On the other hand, overlapping areas are easily formed on boundaries between the pixel arrays if the pixel arrays as a basis are large, whereas it is necessary and complicated to verify optimization for an evaluation target area of the wafer edge part if the pixel arrays are small.